- Sara Laura Wilson
N.A.T.U.R.A.L. (Natural Alternative To UV-Radiation Absorbers: Lignin)
Updated: Jun 8, 2020
Class: Materials Project Laboratory (3.042)
Term: Fall 2019
Two types of sunblock exist on the market: absorption-based and scattering-based. However, current absorbance-based sunblocks contain small molecules that have the potential to be carcinogenic. Moreover, scattering-based sunblocks are chalky in appearance. To address both concerns, our team developed a process for utilizing lignin, a biopolymer UV-absorber, as a natural, clear sunscreen agent. We developed and defined bleaching and testing procedures for lignin, which have shown to decrease lignin’s reflectance of visible light while maintaining some of its UV-absorption. After bleaching lignin, it was incorporated into a carrier (like a moisturizer) for easy testing and application. We performed UV-Vis spectrometry to yield data about transmittance and SPF, which informed the viability of lignin as a competitive alternative to other UV-absorbers.
We chose lignin, the second most abundant natural biopolymer (derived from vascular plants), as our UV-absorber to incorporate into a carrier to create a sunblock cream. As lignin is naturally derived, it is biocompatible. Additionally, it is a byproduct of paper-making processes and is therefore abundantly available.
We developed a successful treatment for lignin that decreased its reflectance of visible light while maintaining its UV absorption. Lignin was bleached with hydrogen peroxide to decrease its absorbance in the visible light range (from about 400nm to 800nm). We quantified these results with UV-Vis spectroscopy.
(Left) Lignin, a plant-derived UV-absorber, is naturally dark brown. When incorporated into carriers (moisturizers like Cetaphil and Olay ), it alters the opacity. At one and two weight percent lignin in carrier, a significant change in pigment is observed. (Right) We developed a bleaching procedure for lignin that increases its transparency, as to not alter the carrier’s pigment, which is transparent when applied to a surface. Our final prototype was the 10 percent H2O2 bleached lignin in Olay carrier at two weight percent (boxed in red). Photo by Sofia Lobo.